Battery storage system with integrated inverter

ABSTRACT

There is provided a power converter unit that can include an inverter and a plurality of batteries. The power converter unit can include a battery energy storage system (BESS) and an inverter. The BESS and the inverter can share at least one protection circuit.

TECHNICAL FIELD

The present invention relates generally to energy storage. Inparticular, the present invention relates to improving costs,reliability, and maintainability of battery energy storage systems.

BACKGROUND

In power generation and energy storage applications, an inverter and abattery energy storage system can be connected together to form a powergeneration unit. Although functioning as one system, the battery energystorage system and the inverter are conventionally disposed at differentlocations and interconnected with cables. More specifically, the batteryenergy storage system and the inverter are normally stored in separatehousings. Additionally, each housing includes its own dedicated coolingsystem, thereby increasing the cost of operation.

The separate housings correspondingly increase the complexity. Forexample, the conventional inverter and battery energy storage systemsrequire extra protection circuits as well as additional subsystems tointerface the inverter and battery energy storage system. Due to thecomplexity in these interfaces, these conventional routinely experiencefailure in several stages, creating reliability problems. Thesereliability problems further increase the costs of deploying andmaintaining these systems in the field.

SUMMARY

The embodiments featured herein help solve or mitigate the above-noteddeficiencies. The embodiments provide at least the following advantages.They reduce the overhead on the cooling hardware required, thus reducingthe need for maintenance. Due to their compactness, shipping of theexemplary systems can be more efficient and production costs can bemitigated. Specifically, the total reduction in size and footprintprovided by the exemplary systems can reduce length and cost of directcurrent (DC) wiring. These reductions minimize the need for distributedprotection circuitry as well as distributed lock out/tag out (LOTO)systems.

Furthermore, the embodiments can provide added environmental protectionfor an inverter. Specifically, optimal ambient conditions for thebatteries (e.g. about 25 degrees Celsius) in a battery energy storagesystem are also nearly ideal for the power electronics componentsincluded in the inverter. As such, the embodiments can provide anintegrated system where both the inverter and the batteries operateunder the same controlled environment. In addition to having similarambient requirements, the inverter and battery energy storage systemscan have similarly matched duty cycles. The embodiments can also providematched duty cycles that allow the inverter and the battery energystorage system to function on the same electrical system, as describedin more detail below.

One embodiment provides a system that can include a battery energystorage system (BESS) and an inverter. The BESS and the inverter canshare at least one protection circuit.

Additional features, modes of operations, advantages, and other aspectsof various embodiments are described below with reference to theaccompanying drawings. It is noted that the present disclosure is notlimited to the specific embodiments described herein. These embodimentsare presented for illustrative purposes. Additional embodiments, ormodifications of the embodiments disclosed, will be readily apparent topersons skilled in the relevant art(s) based on the teachings provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments may take form in various components andarrangements of components. Illustrative embodiments are shown in theaccompanying drawings, throughout which like reference numerals mayindicate corresponding or similar parts in the various drawings. Thedrawings are for purposes of illustrating the embodiments and are not tobe construed as limiting the disclosure. Given the following enablingdescription of the drawings, the novel aspects of the present disclosureshould become evident to a person of ordinary skill in the relevantart(s).

FIG. 1 illustrates a power converter unit, according to an embodiment.

FIG. 2 illustrates a view of a power converter unit, according to anembodiment.

FIG. 3 illustrates an inverter, according to an embodiment.

FIG. 4 illustrates a circuit according to various aspects disclosedherein.

FIG. 5 illustrates an aspect of the subject matter in accordance withone embodiment.

DETAILED DESCRIPTION

While the illustrative embodiments are described herein for particularapplications, it should be understood that the present disclosure is notlimited thereto. Those skilled in the art and with access to theteachings provided herein will recognize additional applications,modifications, and embodiments within the scope thereof and additionalfields in which the present disclosure would be of significant utility.

FIG. 1 illustrates a power converter unit 100, according to anembodiment. The power converter unit 100 include an enclosure 101 thathouses a plurality of batteries 104. The enclosure 101 also houses aninverter 112. That is, the plurality of batteries 104 and the inverter112 are co-located in the single enclosure 101.

The batteries 104 can be distributed in a plurality of battery sections102 of the enclosure 101. Each section can include racks and cables thatrespectively support the batteries 104 and provide electricalconnections to their terminals.

The power converter unit 100 can further include a thermal managementsystem 106 configured to regulate the temperature inside the enclosure101. In one embodiment, the thermal management system 106 provides anair flow within the enclosure 101 to cool the plurality of componentstherein.

At least one component or section of the inverter 112 can be thermallyisolated from the thermal management system 106. For example, onesection of the inverter 112 can be cooled using outside air or withanother thermal management system (not shown). In one exampleimplementation, air vents 108 and 110 are provided on a front panel of asection of the inverter 112. The air vents 108 and 110 can be thermallyisolated from other components of the inverter 112 and from theenvironment inside the enclosure 101. As described below, at least onesection of the inverter 112 can be thermally isolated from othersections to optimize the thermal loading.

The at least one thermally isolated section can be a cabinet of theinverter 112 that includes magnetic components. Specifically, thethermal isolation of a magnetics cabinet of the inverter 112 and thereturn duct collecting heat directly from the IGBT cabinet of theinverter 112 can protect the battery cells from hot spots. When somecells are hotter than others, the internal resistance of the hottercells increase significantly faster than the cooler cells. This createsan imbalance in the resistance of the multi-parallel strings, which inturn reduces the total energy harvestable from the system. As such,thermal isolation can help mitigate this issue. In sum, the batteries104 and at least one section of the inverter 112 can be cooled (orthermally managed) together, i.e. by a common thermal management system.

By way of example only, and not limitation, the thermal managementsystem 106 is configurable to set the temperature inside to theenclosure 101 at about 25 degrees Celsius. Generally, the thermalmanagement system 106 can be configured to set the temperature to withina tolerance interval of a nominal temperature. For example, the thermalmanagement system 106 can set the temperature inside the enclosure 101to 25 degrees Celsius with an allowable tolerance interval of plus orminus five degrees around 25 degrees Celsius.

In the embodiments, the thermal management system 106 can be any coolingsystem known in the art. For instance, the thermal management system 106can be a heating, ventilating, and air conditioning (HVAC) system, andcan operate utilizing feedback from a thermostat to actively regulatethe temperature inside the enclosure 101.

Without limitation, the power converter unit 100 can include a BESS. TheBESS can include one to many batteries enclosures, inverters,transformers, switch gears, and controllers needed to operate andprotect the BESS when connected to a single interconnection point.

Furthermore, a battery enclosure such as the enclosure 101 can include aplurality of battery modules, battery racks, HVAC systems configured forthermal management. The enclosure 101 could also include a firesuppression system, a building control system, a battery interfacecabinet, auxiliary transformers, meters, a low voltage panel, as well assignal and power cabling. Additionally, the plurality of batteries 104can include one or more lithium ion batteries.

The BESS can be scaled for applications ranging from a fraction of aMega Watts (MW) to 100 MW to meet power and energy capacityspecifications. Meeting such specifications can be tied directly to bothcharacteristics of the power converter unit 100 and the maximum numberof such power converter units that a plant controller can drive.

In the embodiments, the inverter 112 can have a minimum power outputcapacity of 0.25 MW. Thus, when scaling, the minimum incremental sizeper power converter unit can be 0.25 MW. Typically, a plant controllercan drive at most 40 MW. As such, 32 power converters can be used toreach 100 MW, requiring at least three plant controllers.

FIG. 2 illustrates a view 200 of the power converter unit 100, accordingto an embodiment. As shown in FIG. 2, the inverter 112 fits within theenclosure 101 without taking substantially more space than needed tohouse the plurality of batteries 104. Stated otherwise, viewed from theside, when the power converter unit 100 has a length represented by thebracket 202, a side panel of the inverter 112 consumes only a smallportion of that length. As such, by including the inverter 112 withinthe enclosure as the batteries 104, a single thermal management systemcan be used to cool both the inverter 112 and the batteries 104. In anembodiment, the inverter 112 occupies about 10% of the volume of theenclosure 101. In other embodiments, the inverter 112 occupies less than10% of the volume of the enclosure 101. Moreover, the inverter can beplaced at an extremity of the enclosure 101, thus allowing for externalaccess of the inverter components.

FIG. 3 depicts a view 300 of the inverter 112, according to anembodiment. Doors or front cover panels of the inverter 112 are notshown in order to illustrate an exemplary implementation. In the exampleof FIG. 3, the inverter 112 includes a control cabinet 302, a bridgecabinet 304, a magnetic element cabinet 306, and an input output (I/O)cabinet 308. When the inverter 112 is integrated with a battery energystorage system, the inverter 112 may not necessarily have doors or frontpanels. Doors can be added for additional security.

The control cabinet 302 can include a plurality of components configuredto provide functionality to the inverter 112. For example, the controlcabinet 302 can include components that interface with an electricitygrid to deliver alternating current (AC) power produced by the inverter112. The control cabinet 302 can also include circuitry for drawing DCpower from the batteries 104 to power to other stages of the inverter112 for subsequent conversion to AC.

The bridge cabinet 304 can include power conversion and signalconditioning circuitry typically found in inverter topologies known inthe art. In general, the bridge cabinet 304 can include powerelectronics elements, such as insulated gate bipolar transistors(IGBTs), flyback diodes, controllers, and the like, which provide powerconversion.

The magnetic element cabinet 306 includes a plurality of magneticelements, such as transformers and inductors. The magnetic elements canbe vacuum impregnated with environmental varnish, thus providing moreresistance to environmental degradation.

In the exemplary implementation of the inverter 112, the magneticelement cabinet 306 can be thermally insulated from the other cabinetsof the inverter 112. That is, the magnetic element cabinet 306 can bethermally isolated from the other constituent parts of the inverter 112.

In the exemplary embodiment of the inverter 112, the thermal timeconstant for the power electronics components of the bridge cabinet 304,such as IGBTs, can amount to 40% of the total thermal load of the powerconverter unit 100, and the thermal time constant for the powerelectronics components must typically be in the order of minutes toensure proper functioning.

Conversely, the thermal time constant of the magnetic elements can be ofthe order of hours, and it can also potentially exceed the batterydischarge time. Accordingly, thermally isolating the magnetic elementcabinet 306 from the other components, specifically from the bridgecabinet 304 and the batteries, can ensure proper thermal management ofthe inverter 112. Proper thermal management is advantageous since theinverter 112 is co-located with the plurality of batteries 104 and canbe managed by a common thermal management system.

The I/O cabinet 308 can include a plurality of input and output hardwarethat provide one or more interfaces to the other components of theinverter 112. This hardware can be used for measurement, control, anddata acquisition, as well as for scheduling, shutting down, and/orresetting of one or more subsystems of the inverter 112.

In FIG. 3, in each of the cabinets shown, temperature-sensitivecomponents can be arranged for receiving cooler air. For example, in thebridge cabinet 304 the components that dissipate the most heat can beplaced on the top side of the cabinet so they can receive cooler air bybeing closer to vents and ducts of the thermal management system 106.

By including the inverter 112 with the batteries 104 in the sameenclosure, the embodiments permit cooling the batteries and the powerelectronics while segregating the magnetic elements into their owncabinet and rejecting their heat to the exterior of the unit (throughair vent 108 and 110). This heat exchange at the magnetic elementcabinet 306 can be performed by pulling heat from the bottom andrejecting it from the top with minimal filtration. As such, theembodiments allow the cooling loads for an inverter to be nearly halvedrelative to the cooling loads of typical power conversion units.

The inverter/battery integration provided by the embodiments means thatan inverter will be environmentally “ready” for fast start. An inverterplaced by itself outdoors must perform environmental checks and musteither heat or cool itself for some period of time to make sure thevarious electronics are in the correct conditions to start operating atfull power. In contrast, in the embodiments, the inverter and thebatteries can be kept in a thermal zone that is also ideal for theinverter at all times. As such, the inverter can function without everrunning additional heating or cooling functions, and without waiting fora dispatch that may allow only a few seconds or even milliseconds totake action without running an additional environmental conditioningsystem.

The inverter 112 can further include several electrical characteristicsthat facilitate its integration as part of a battery energy storagesystem. Moreover, these electrical characteristics can allow theinverter 112 to function as part of the same electrical system as thebatteries 104 and their associated support systems.

FIG. 4 illustrates the circuit schematic of an inverter 400 according toa typical configuration where the batteries of a BESS battery bank 408and the BESS inverter 400 are not co-located. Instead they are housed intwo separate cabinets, separated by a distance. The BESS inverter 400 isconnected to the BESS battery bank 408 by cables 410. Because of thisseparation between the two cabinets, protection against a lightningstrike must be provided at each end of the cables 410 by lightningprotection devices 402, 404, 414 and 416 at each end of the two DCcables 410.

The inverter 400 includes a DC-DC converter 418 configured to regulateDC power for storage in a battery bank 408, and an inverter 422 tocondition signals and perform power conversion from DC to 3-phase AC.Between these two sections is a DC capacitor bank 420. Furthermore,there is provided an AC filter that includes inductor 424 and capacitor426. A DC disconnect switch and/or LOTO device 412 is included betweenthe inverter 400 and the BESS battery bank 408 because of the separationbetween the two cabinets. Moreover, there is also included a DCdisconnect switch and/or LOTO device 430 between the inventor and a MVtransformer 434. The BESS inverter 400 and the MV transformer 434 arehoused in two separate cabinets, separated by a distance, and connectedby cables 432. Consequently, protection against a lightning strike mustbe provided at each end of cables 432, by lightning protection devices427 inside BESS inverter 400 and (not shown) inside the MV transformer434.

FIG. 5, on the other hand, illustrates an exemplary circuit schematic ofan inverter 500, like the inverter 112, co-located with batteries of aBESS battery bank 508. The inverter 500 includes a DC-DC converter 518configured to regulate DC power for storage in the BESS battery bank508, and an inverter 522 to condition signals and perform powerconversion from DC to 3-phase AC.

Between these two sections is a DC capacitor bank 520. Furthermore,there is provided an AC filter that includes inductor 524 and capacitor526. A DC disconnect switch and/or LOTO device 512 is included betweenthe inverter 500 and the BESS battery bank 508, and no other DC switchor LOTO devices are used. As such, in the inverter 500, only one LOTOdevice 530 is used and only one protection device 528 is used. Theinverter 500 is then connected to the MV transformer 534 by a cable 532.Therefore, in the inverter 500, the battery energy storage system 508and the inverter 522 share at least one protection circuit and share atleast one LOTO device. In other words, the inverter 500 can beimplemented with fewer components than the inverter 400.

Those skilled in the relevant art(s) will appreciate that variousadaptations and modifications of the embodiments described above can beconfigured without departing from the scope and spirit of thedisclosure. Therefore, it is to be understood that, within the scope ofthe appended claims, the disclosure may be practiced other than asspecifically described herein.

1. A system, comprising: a battery energy storage system (BESS); and aninverter; a thermal management system that cools the BESS and theinverter; wherein the BESS and the inverter share at least oneprotection circuit.
 2. The system of claim 1, further comprising asingle lock out/tag out (LOTO) system.
 3. The system of claim 2, whereinthe LOTO system is disposed at an output stage of the inverter.
 4. Thesystem of claim 1, wherein the inverter and the BESS are co-located inthe same enclosure.
 5. The system of claim 1, wherein the inverter has aminimum output of 250 kW.
 6. The system of claim 1, further comprising aplurality of batteries includes a lithium ion battery, or otherchemistry.
 7. (canceled)
 8. (canceled)
 9. The system of claim 1, whereinthe inverter and the BESS are configured to operate on the sameelectrical system.
 10. The system of claim 1, wherein the inverter theBESS have matched duty cycles.
 11. The system of claim 1, furthercomprising at least one section thermally isolated.